That is not possible, because the User Agent (UA) does not return a simple boolean value to the endpoints that requests attestation.That endpoint requests a cryptographic proof that originates at a shared root of trust between that endpoint and the device you are using (which has an embedded secret that its user cannot extract, and which was blessed by this shared root of trust with a cryptographic signature at the device's factory). Being able to generate that proof will attest that your device, its operating system, the software it has installed, as well as the UA have all been deemed acceptable (i.e., cryptographically signed by something/someone that root of trust has extended its trust to) by the attestation arbiter - so probably either Apple, Google, or Microsoft.